Tricks of the Wizards

Function Tracing Again

Filter::Simple can help out with the parsing a little
Suppose we'd like to instrument each function to announce itself when it's called
It is sufficient to have each function call 'trace':

        sub trace {
          ($package, $file, $line, $subr) = caller;
          my $depth = 0;
          1 while defined caller(++$depth);
          my $indent = "  " x ($depth - 2);
          local $" = ', ';
          print "$package\::$subr(@_)\n";
        }

Our source filter will find this:

        sub something {
          ...

And replace it with this:

        sub something {
          &Trace::trace;
          ...